Significance of commonly used prognostic factors differs for children withT cell acute lymphocytic leukemia (ALL), as compared to those with B-precursor ALL. A Pediatric Oncology Group (POG) study

T cell acute lymphocytic leukemia (T-ALL) and B-precursor ALL differ signif icantly in the clinical characteristics of the patients at presentation and in laboratory-defined characteristics of the leukemic cells. We assessed f or pediatric patients with T-ALL the relative importance of prognostic fact ors previously demonstrated to predict outcome in B-precursor ALL. Presenti ng clinical and laboratory features were correlated with outcome for 441 ch ildren 12 months to 21 years of age with previously untreated T-ALL, regist ered on the Pediatric Oncology Group (POG) T3 protocol between 1986 and 199 2. These T-ALL prognostic factor analyses were then compared to similar ana lyses for 1993 patients with B-precursor ALL enrolled during the same time period on the FOG ALinC 14 protocol. Quantitative interaction between pheno type and each prognostic factor was studied to determine the relative impor tance of the prognostic factor for each of the two major immunophenotypes. We also analyzed the importance of maturational stage as a T-ALL prognostic factor, using a modified Ludwig definition of maturational stage. We concl ude that several of the clinical and laboratory prognostic factors, which a re used reliably for B-precursor ALL, are much less predictive in T-ALL (ie age, WBC, consensus risk group, hyperdiploidy, presence of translocations and CALLA expression). There was no significant difference between the phen otypes in the prognostic importance of race or gender. Our data demonstrate a significant difference in outcome among the three maturational stages of T-cell ALL, with the intermediate group faring best. Using traditional ris k group criteria to stratify patients with T-ALL for therapy may not be app ropriate.